Avalanche Forecast

Kootenay Boundary

Date issued

Mar 31, 2018 - 3:28 PM

Valid until

Apr 1, 2018 - 2:00 PM

Prepared by

mgrist

Moderate to strong northwest / southwest winds have created wind slabs at upper elevations. These may be most reactive on shady aspects. Reduce your exposure to sunny slopes if the sun makes an appearance.

Regular season
Saturday - March 31, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Sunday - April 1, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Monday - April 2, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Avalanche Problem 1: Wind Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Northwest then southwest wind formed wind slabs, which could be most reactive on shady aspects where they may be sitting on weak surface hoar or facets.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Extra caution needed around cornices with current conditions.

Avalanche Summary

On Friday, cornice control work resulted in triggering a size 2 wind slab below, on an east aspect near 2200m. Slab depth averaged 20cm.

Tuesday's reports focus on a few natural storm slab avalanches size 1.5-2 on northeast and northwest aspects at 2200m.

On Monday there were reports of numerous explosives and naturally triggered storm slab avalanches size 1.5-2 on all aspects in the alpine and tree line.

Snowpack Summary

Warm temperatures and sun over the long weekend resulted in moist surface snow on sunny aspects, and firm crusts when the surface froze overnight.

30-60 cm of snow from last week sits on a crust at all elevations on solar aspects and all aspects below 1900 m elevation. Winds were moderate to strong from the north west on Wednesday (switching to southwest by Friday), creating fresh wind slabs on down wind (lee) aspects at higher elevations.

On northerly aspects at and above tree line the old storm snow is burying a mix of large surface hoar and surface facets. Another weak layer buried mid March is down 50 to 80cm and is a crust on solar aspects and surface hoar (to 6mm) on high elevation north. The surface hoar is still giving sudden collapse test results.

A few other persistent weak layers are buried in the mid and lower snowpack, but they have gone dormant and are unlikely to resurface until we move into a period with consecutive above-freezing nights.

Weather Forecast

Forecast amounts of new snow are uncertain on Sunday into Monday. Temperatures are staying cool for this time of year.

SUNDAY: Cloudy with some flurries (5-10 cm during the day; another 10cm overnight) / Light to moderate south west wind / Alpine temperature -5 / Freezing level decreasing to 1300m

MONDAY: Cloudy with some lingering flurries / Light to moderate northwest wind / Alpine temperature -7 / Freezing level 1000m

TUESDAY: A mix of sun and cloud / Light to moderate west wind / Alpine temperature -4 / Freezing level 1500m

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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